The present invention relates to video editing, and more particularly to a spiral buffer for non-linear editing where a video signal is simultaneously converted from a linear to a non-linear format while being cataloged by an operator.
A linear editing system uses a linear video source, such as a camera or video tape recorder. As the video is played from the linear video source, an operator, either with manual annotations and/or computer assisted annotations, catalogs the material presented by the video. Cataloging is a process by which the operator identifies segments of the video that are to be kept or discarded. After the video has been cataloged, then the editing process is used to sort, order, crop and otherwise alter the video that has been kept by the cataloging process. In this manner a large amount of video may be reduced to a desired time frame, for example, reducing five hours of video to a twenty-four minute situation comedy episode.
Since the video source is linear, it has to be played sequentially to arrive at a particular segment of interest. This is time consuming, as it takes time to position video tape through shuttling and jogging operations. With the advent of non-linear storage medium, such as random access video disks, the time to access any particular segment is reduced. However another step in the editing process is added, namely converting the video from a linear form to a non-linear form, also called video capture. This conversion step is added either before or after the cataloging step, which requires the video to be played twice prior to the editing step, once for cataloging and once for capturing for storage. Pictorially the conventional nonlinear editing process may be modeled as follows: EQU CAPTURE&gt;&gt;&gt;CATALOG&gt;&gt;&gt;EDIT&gt;&gt;&gt;OUTPUT
or EQU CATALOG&gt;&gt;&gt;CAPTURE&gt;&gt;&gt;EDIT&gt;&gt;&gt;OUTPUT
The two approaches to capturing the video material involve either capturing all material prior to cataloging, which consumes large amounts of storage space, or capturing after cataloging, which consumes more of the operator's time. In the latter sequence the operator specifically must tell the system to capture the material when he finds a sequence which he may want to keep. The system must then replay the sequence to capture and save it for storage.
What is needed is a non-linear editing process that further reduces the editing time and minimizes the amount of storage space used.